Alright, the electrical water heater is a supply to the heat pump, it will allow you to get some power from the heat pump in severe conditions- without the electrical water heater your pump will simply do defrosting after defrosting :

when a defrosting cycle is performed the water temperature is lowered ( i.e; transformed into heat to de_ice the evaporator)

under severe condition the heat pump will have to recover the lost heat and if it succeeds, it is likely that a the evaporator is frozen again and a new cycle will begin

however under dry and cold conditions, you can defer defrosting cycle and benefit from a COP say around 2...

I have set 22 Supplementary authorization threshold - -7c, but still i can't find how to disable heater alltogether.

As i said in a previous post , the KD60 controller will still trigger the heater if the WRTT is too low, the only way to disable heater is to open the electrical breakers.

Also I have a question - can i turn circulationg pump for heating floors to level 2 or even 1? I believe level 3 that is 200w is too much.

Are you speaking of the pump that is enclosed in the heat pump or do have a buffer tank, from which circulating pumps will distribute the heat to the floors?If changing the speed level of heat pump , you must check that the deltaT stays around 5.if the circulating pump is to fast, the deltaT will go down and possibly trigger an ERROR (E44 i think).Why do you want to change the circulating pump setting?

ouap! but you are really looking for troubles ... you could open the module box, and check if it looks like the drawing attached.If you have no more KD60 control, you can however try to cheat the 2 zones modules: it should be possible to set it into "forced" heating mode. let us see how :

at the upper right corner you have 2 small control boards ( 1 &2 ) that control the operation of circulating pumps1 and 2.

i guess that the way the KD60 control board controls the module boards is by closing or opening a circuit=> you have to try until you are able to run or stop a ciculating pump.

if you would not succeed you would have to set a switch or thermosttat to operate directly the circulating pumps.

No chance, the KD60 board is linked through a BUS wire. So to control the units manually i suggest to do the following:

disconnect from KD60 = look at the small board wire diagram attached and disconnect the BUS connector

test1 : look at the small board wire diagram attached and notice the P1P2 connector, the wires should go to the relay controlling the pumptwo wires from connector P1 & P2 control the circulating Pump =>disconnect the two wires, check how /if they are connected to a relay and apply 220V phase and Neutral on these 2 wires and check if the relay/pump are operatingconclusion : you should be able to operate the circulating pumps

test2 : look at the bottom connector with letters NU Y1 N Y2 : Y1 & Y2 wires control the 3 way valve ( open & close). disconnect Y1 N wires, apply 220V phase to Y1 and N to neutral => the 3WV should operate, if not apply to Y2 and Nconclusion : you be able to operate the 3 way valve, In addition you should operate the 2 3way valves so that the water goes through the associated floors. Leave both 3WV open.

consolidate : use 2 switches to run the circulating pumps and that's it.Now you are operating in forced heating mode and you can only control your TÂ°C by setting it with the HEAT parameter at the heat pump ( or using its waterlaw).

So I've got com to ttl adapter, connected all wires properly gnd, tx, rx and Vcc, but modbus doesn't ant to read it. I have used the burned controller, but it should read anyway, because lower part of controller where the eeprom chip is is not burned. Burned is upper part where transistors, switches and mosfet are.

maybe you have also XP OS with soft 'hyperterminal' included ( also soft as 'putty' ) , so you can try a loopback test to verify the adapter ttl/rs232 ; with jump beetween TX, RX, each caracter stroke on keyboard should be reported to hyperterminal screeen (with function 'echo on' disabled)

if it's ok, we'll have to look what is the matter with ech ;

did you use the Fred28 soft downloaded from forum? i prefer use a classic modbus request software as 'modscan32' or others; this allow to execute some specific commands

I have a lot of computers available, so that is not a problem.Yes, I used XP and computer have COM port.

I have used both software, but no luck. Connected everything properly as in diagram. I have used audio cable that fits adapter and other 4 wires I connected to controller.

Regarding question about removing heater. As I understand, you can buy just the heat pump unit without heater, 2 zone floor heater and kd60 unit. That means that it will frost up anyway and it is necessary to have heater when using this heatpump in colder conditions?What would you reccomend - try to repair it, buy new heater(150Eur in this forum), buy new water pumps so that 2 zone heating works properly or just leave it as it is while it works and then replace everything with new and more modern heatpump?

I ordered USB to TTL adapter but this also doesn't seem to work.Main problem now is that heat pump shows E41 error. I have opened circulating pump scrtew and turned it manually, it turns without problems. When I trigger the switch in Siemens relay(M3), pump turns on and everything is fine, but it works only when i hold the trigger on relay.

E41 means low water flow or not more flow...Well it could also mean the flowmeter is nomore working, or the pump relay is dead, or ....but any way you shoud check first your water circuit, especially the inflow filter which should be at machine water entrance.To check the flow meter ( blue device , see attached picture) :